Ytterbium triflate catalyzed synthesis of chlorinated lactones

The direct synthesis of chlorolactones from differently substituted alkenoic acids, using either sodium hypochlorite or chloramine T as the source of electrophilic chlorine and ytterbium triflate hydrate as the Lewis acid is described. In both cases the reactions proceeded in good yields affording selectively five- or six-membered chlorolactones.     

A Morita-Baylis-Hillman adduct allows the diastereoselective synthesis of styryl lactones

We disclosed herein a diastereoselective approach for the total syntheses of (±)-Leiocarpin A and (±)-Goniodiol. These biologically active styryl lactones were obtained from a common intermediate, prepared in five steps and 40% overall yield, using a simple synthetic sequence starting from a Morita-Baylis-Hillman adduct. The total syntheses of these styryl lactones were accomplished in nine steps. This is the first report on the total synthesis of this class of natural products starting from Morita-Baylis-Hillman adduct.     

A domino ring-closing metathesis as a key-step in the synthesis of chiral lactones from d-mannitol

Chiral lactones were synthesized in six steps from d-mannitol. The key-step was a domino ring-closing metathesis reaction leading to the symmetric cleavage of a d-mannitol triene derivative and to the formation of two molecules of the desired lactone.     

A phenyldilactone,bisnorsesquiterpene, and cytotoxic phenolics from Maytenus senegalensis leaves

Maytenus senegalensis Lam. (Celastraceae) leaves are traditionally used in West Africa for the management of cancer and other disorders associated with inflammation. In this study, bioactivity-guided fractionation of the methanol leaf extract of Maytenus senegalensis led to the isolation of 11 compounds, including the new phenyldilactone, maysedilactone (1). All isolated compounds were tested for cytotoxicity against mouse lymphoma cell line (L5178Y). Only (−) epigallocathechin showed high cytotoxicity and completely inhibited cell growth at the investigated dose of 10 μg/mL. This result supports the claimed efficacy of Maytenus senegalensis leaf extract in ethnomedicinal treatment of cancer.     

Facile conversion of lactols to lactones using IBX

Lactols, which are insoluble or only sparingly soluble in most of the organic solvents that are generally employed for oxidation, are converted to lactones using o-iodoxybenzoic acid (IBX) in a facile manner under modified experimental conditions [EtOAc-DMSO (9:1) mixture at reflux] in good to excellent isolated yields (66-91%).     

Design and synthesis of novel cytotoxic podophyllotoxin derivatives

<正>In order to investigate the effect of different C4 linkage moieties on the cytotoxicity of podophyllotoxin derivatives,novel 4-Nand 4-C-substituted 4'-O-demethylepipodophyllotoxin derivatives were designed and synthesized.All the compounds were tested against A549 and MCF-7 tumor cells in vitro,and six compounds showed significant cytotoxicity.The most active compound 9f was superior to GL-331,and exhibited potent cytotoxicity with IC_(50) value at 10~(-7) mol/L level.     

Total synthesis of the marine cytotoxic caulibugulones A-D

We report the first total synthesis of the cytotoxic marine alkaloids caulibugulone A-D. This synthesis confirmed the assigned structures and provided sufficient material for further biological testing.     

Nitrogen ylide-mediated cyclopropanation of lactams and lactones

Cyclopropanation of α,β-unsaturated δ-lactams and δ-lactones mediated by nitrogen ylides is described. The process tolerates different alkyl halides and gives efficiently bicyclo[4.1.0]heptanes in a totally stereoselective manner. On the other hand, ε-lactams under our experimental conditions suffer a novel process involving a skeletal reorganization to give a bicyclic[3.3.0] system.     

Facile synthesis of lactones and dihydronaphthalenes from methyl 2-isobutenyl (or 2-isopentenyl)cinnamates as the common intermediates

We prepared three different types of compounds, two α-alkylidene-γ-butyrolactones and 3,4-dihydronaphthalene-2-carboxylic acid from methyl 2-isobutenylcinnamates or methyl 2-isopentenylcinnamates as the common intermediates, which were derived from the acetates of Baylis-Hillman adducts.     

On the synthesis of cepacin A

Efforts directed toward a total synthesis of cepacin A is presented in full detail. The C-7, C-8, and C-9 stereogenic centers in the target molecule were derived from d-arabinose. The configuration of the allene axis was controlled at the bromoallenation step by the C-10 configuration of the precursor. An unexpected yet very interesting phenomenon was observed with the bromoallenation, where the α-isomer of the propargylic alcohol 31 was entirely resistant to the conditions that worked so well for its β-counterpart. The problem was eventually solved by careful tuning of the size of the neighboring groups based on the clue obtained from conformational analysis. The diyne moiety was incorporated into the molecular framework through a coupling of the TMS protected diyne with a proper bromoallene under the Sonogashira conditions with EtOAc as the solvent. Use of other solvents at this step led to complete failure.     

Online ATR-IR investigations and mechanistic understanding of the carbonylation of epoxides - the selective synthesis of lactones or polyesters from epoxides and CO

In situ ATR-IR spectroscopy is applied as a powerful tool to study the factors that control the reaction of epoxides with carbon monoxide in the presence of [Lewis acid]⁺[Co(CO)₄]⁻ salts. Based on these investigations, a consistent mechanistic scheme is presented, comprising the main lactone and polyester products and minor components, e.g., acetone and crotonic acid derivatives. β-Alkoxy-acyl-cobalttetracarbonyl species are shown to be key intermediates from which two reaction routes start in dependence of the applied Lewis acid (LA). Labile LA-alkoxy combinations favor a backbiting process of the oxygen function on the Co-acyl bond, primarily producing lactone products. More stable LA-alkoxy entities are unreactive toward PO conversion and afford a polymerization reaction after the addition of a nucleophile. In that case, the Lewis acid remains bonded to the chain end.     

The synthesis and cytotoxic activity of novel organogermanium sesquioxides with anthraquinone or naphthalene moiety

Four novel organogermanium sesquioxides with anthraquinone or naphthalene moiety were synthesized.The structures were characterized by IR,NMR and elemental analysis,and their cytotoxicities were evaluated against human chronic myeloid leukemia K562 cell lines.The cytotoxicity could be improved by the introduction of planar aromatic chromophore moiety to the parent compound,Ge-132.     

Hydroperoxide and endoperoxide lactones from photooxygenation of 3-alkylidenedihydrofuran-2,4-diones

3-Alkylidenedihydrofuran-2,4-diones 1 can be photooxygenated with O(2)/TBHP to hydroperoxides 3 which slowly decompose to diols 5. Stable endoperoxides 4 are best prepared by photooxygenation of 1 with 2 equiv of O(2) in the presence of CuSO(4) and p-TosOH following a nonradical mechanism. They are rapidly reduced by anhydrous FeBr(2) to give butenolide 9 indicating a potential antimalarial activity.     

A simple route to the syntheses of both enantiomers of trans-oak lactone and (+)-cis-oak lactone

Stereocontrolled syntheses of both enantiomers of trans-oak lactone and (+)-cis-oak lactone have been achieved from a common precursor.     

A cytotoxic compound from the leaves of Juglans mandshurica

From Juglans mandshurica leaves, a new quinone compound was isolated through bioassay-guided fractionation. The structure elucidation of the compound was established based on spectroscopic studies, notably of the 2D NMR spectra. The compound exhibited moderate cytotoxic activities against Hela, MCF-7, BGC823 and 3T3-Llcell lines with IC50 ranges from 7.5 to 26.8 μmol/L.     

Divergent synthesis of cytotoxic styryl lactones from D-xylose. The first total synthesis of (+)-crassalactone C

A new divergent approach to (+)-goniofufurone (1) and 7-epi-(+)-goniofufurone (2), as well as the first total synthesis of crassalactone C (3), has been achieved starting from D-xylose. In a preliminary bioassay, all three natural products 1, 2, and 3 showed remarkable in vitro antiproliferative activities against K562, Raji, and HeLa neoplastic cell lines.     

A new cytotoxic bufadienolide from Chinese medicine Chansu

A new cytotoxic bufadienolide was isolated from the traditional Chinese medicine-Chansu. The structure of new compound was elucidated on the basis of spectral methods including 2D NMR. And it showed strong in vitro cytotoxic activity against Hela cells with IC50 of 8.06 × 10^-2μmol/L.     

Synthesis of 2, 5-disubstiututed tetrahedrofurans from organozinc halides and lactones

2,5-Disubstituted tetrahydrofurans were obtained from lactones and organozinc halides in moderate to high yield in the presence of Lewis acids.     

An unusual palladium-catalyzed carbonylative cyclization of β-bromovinyl aldehydes leading to lactones

β-Bromovinyl aldehydes are carbonylatively cyclized under carbon monoxide pressure in MeCN at 100 °C in the presence of a catalytic amount of a palladium catalyst along with a base to give the corresponding lactones in high yields.